1. Field of the Invention
This invention relates in general to fluorescent backlit displays and more particularly to such displays which are especially adapted for use in trade shows.
2. Description of the Prior Art
Trade show displays prior to 1970 were primarily custom type, made of wood, metal and plastic in heavy three dimensional form. Light weight portable displays emerged in the 1970s built around aluminum frames and spokes to serve manufacturers who chose to set up their own exhibits to save labor costs. Such displays were often clad with loop fabric to which all manner of graphic sheets were attached with hook type fastener strips. To attract attention, such displays were often fitted with spotlights that flood the graphic surfaces with light and heat.
While the best presentation of any image was known to be backlit lighting through a translucent image, little use of backlit imagery was the practice until recently. Photographic films were too fragile for knockabout trade show use; and traditional light boxes were rigid massive structures. Kodak technical manuals suggested that good back light design (for acceptable light uniformity) required lamps to be positioned behind the graphic film a distance greater than the lamp to lamp separation.
Early forms of larger backlit displays utilized images formed on fabric or plastic sheeting suspended on the front members of a space frame. Lighting was provided by several common one or two lamp fluorescent lamp units suspended on the rear side of the space frame. Space frames were typically 12 to 16 inches deep to provide stability. Image luminance (or brightness) was typically low, i.e., in the 100 foot lambert range.
My U.S. Pat. No. 5,282,117, dated Jan. 25, 1994 discloses an unique lamp masking system that provides extremely uniform display brightness from lamp arrays in which the lamp-to-image distance is substantially less than the lamp-to-lamp distances. With such masking, light boxes only 5 inches deep are now commercially available, providing brightness of the order of 300 foot lamberts in which the brightness variation between lamps is of the order of less than three percent.
Another significant development is the emergence of very large format electronic imaging producing very large color images of quality comparable to or exceeding that of the photographic transparency. In addition, laminating techniques have been introduced for applying strong polycarbonate sheeting to phototransparencies and ink-jet image substrates, enabling them to withstand handling and to be rolled easily for shipment.